We probably need age limits for Senators. When these guys get 80 years of age they are NOT doing an honest day’s work.
I don’t think old age is necessarily bad in itself. It depends on the person. Queen Victoria was still doing a good job in her last years, and I can think of several Popes who continued to do good jobs, including the present one.
I do agree that Senators should step down when they are past it, whether it’s a matter of age, or simply a growing fondness for corruption. If Orrin Hatch loses, it will not be his age so much as a decision by the voters that he is no longer the person he used to be.